JPH05273532A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To lessen the influence of a heat history in a process for assembling substrates and to lessen the restriction on the process temp. in the process by confining the difference in the coefft. of thermal expansion between the two substrates within a specific value. CONSTITUTION:Two sheets of the substrates are disposed to face each other at a desired spacing and a liquid crystal is encapsulated therebetween. The materials of these two substrates vary and the difference in the coefft. of thermal expansion of these substrates is confined within + or -50% of the coefft. of thermal expansion of the one substrate. A thermosetting adhesive 2 is formed by screen printing on the substrate 1 in such a case. On the other hand, resin balls 3 of 7mu spherical diameter for maintaining the prescribed inter-substrate spacing are sprayed onto the substrate 1' and thereafter, an ultraviolet curing adhesive 6 is applied by a precision discharger to the prescribed position exclusive of the region to be used as a liquid crystal display in the final. The two substrates are then superposed on each other in the prescribed position while the marks for superposing formed on both substrates at the time of forming electrodes thereon are checked with a microscope by using a superposing device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display device (LC
D) and a liquid crystal element used for a liquid crystal light valve (LCLV) for a liquid crystal printer.

[0002]

2. Description of the Related Art A general liquid crystal element has a structure in which a liquid crystal material is sandwiched between two substrates and the peripheral portion of the substrates is sealed with a sealant.

Conventionally, substrates of the same type have been used as the two substrates. On the other hand, active matrix LCD
When a Si wafer is used as the TFT substrate as described above, the same Si wafer cannot be used as the other substrate because the Si wafer is non-light transmissive, and a transparent substrate is used instead. It was Also, as a TFT substrate, S
Even when quartz glass is used instead of the i-wafer, an inexpensive transparent substrate is used as the other substrate in consideration of production costs.

[0004]

However, Corning # 70, which is commonly used as a low alkali glass, is used.
No. 59 has a thermal expansion coefficient greatly different from that of the Si wafer, and when both substrates are bonded and thermoset, thermal strain remains,
Problems such as cell warpage occur and it is difficult to manufacture a good liquid crystal device, which is one of the factors that hinder the improvement of yield.

On the other hand, in order for the liquid crystal element to sufficiently exhibit the desired high performance, it is necessary to use substrates of different materials (including those having different compositions and crystal structures) as needed.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned technical problems and to provide a liquid crystal element in which adverse effects due to thermal strain on two substrates are unlikely to occur.

Another object of the present invention is to improve the manufacturing yield of a high-performance liquid crystal device using two substrates made of different materials and to provide the liquid crystal device at a low cost.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal device in which two substrates are opposed to each other at a desired interval and liquid crystal is sealed between them, and the materials of the two substrates are different from each other. This is achieved by a liquid crystal element characterized in that the difference in the coefficient of thermal expansion of the substrates is within ± 50% of the coefficient of thermal expansion of one of the substrates.

According to the present invention, the displacement of the substrate or the displacement of the liquid crystal cell is less likely to occur under any use environment,
In addition, it is possible to prevent a decrease in yield due to the occurrence of the above deviation even during manufacturing.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The combination of substrates used in the present invention is such that the difference in the coefficient of thermal expansion between them is within ± 50%, more preferably within ± 10%, and most preferably Is preferably within ± 5%.

Specifically, when a Si wafer (coefficient of thermal expansion at 227 ° C .: 36.1 × 10 ^-7 / ° C.) is used as one of the substrates, Corning # 1733 (36.5) is used.
× 10 ⁻⁷ / ° C.), Corning # 1729 (35 × 1)
0 ^-7 / ° C), Asahi Glass Co. AL (37 x 10 ^-7 / ° C), N
NA-35 (37 × 10 ⁻⁷ / ° C.) manufactured by H Techno Glass Co.,
One glass selected from the following.

In the present invention, the coefficient of thermal expansion can be measured by a differential expansion meter which measures the difference in expansion between the sample and the standard body made of quartz glass in relation to the temperature.

A method using a dial gauge and a method using a differential transformer are generally used as a method of measuring the displacement due to thermal expansion.

As an example, when a 6-inch Si wafer is used and the cell assembly process temperature is changed from 25 ° C. to 200 ° C., the amount of elongation is 94.9 μ for SiWafer and 97.1 μ for AL. It can be seen that the difference between the two is as very small as 2.2 μ and that pixel deviation is unlikely to occur. on the other hand,
Conventionally commonly used # 7059 has an elongation of 12
The difference from the Si wafer is 3.4 μ, which is very large at 29 μ.

When the above substrate is used for a light transmission type liquid crystal element, it is desirable to use transparent quartz glass as one substrate. On the contrary, in the case of an active matrix type liquid crystal element having a high performance active element, quartz glass may be used, but it is more preferable to use an opaque semiconductor substrate such as an Si wafer as one substrate.

Further, in the case of an active matrix type and light transmissive liquid crystal element having a high performance active element, a translucent insulating film is formed on a semiconductor substrate, and a substrate under the film is formed. It is desirable to use a partially transmissive semiconductor substrate with a part removed. Here, the partially transmissive substrate will be described. FIG. 1 shows a partially transmissive substrate 10.
FIG. 2 is a schematic cross-sectional view showing 0, where 110 is a light transmitting portion and 111 is a non-light transmitting portion. Such a substrate 100 includes a light transmitting layer 104 and an opaque layer 107 for forming the light transmitting portion 110, and the respective film thicknesses have a relationship of T _SI > T _OX . As the light transmission layer 104, an insulating layer such as a silicon oxide film, a silicon nitride film, or a laminated film thereof is preferably used.

On the other hand, as the opaque layer 107, a semiconductor layer such as silicon is preferably used. And the light transmission layer 10
Electrodes for forming a liquid crystal element, wirings, and if necessary, an alignment film and an active element are provided on the surface 4.

FIG. 2 is a schematic sectional view showing a liquid crystal element in which the other substrate 200 is provided on the substrate 100 shown in FIG. 1 with the liquid crystal material 206 interposed therebetween. Here, the difference in the coefficient of thermal expansion between the opaque layer 107, which is the main supporting portion of the substrate 100, and the substrate 200 is within 50% of one substrate, preferably within 10%, and optimally within 5%.

More preferably, in order to form a liquid crystal element,
Active matrix portion 20 including thin film transistors as active elements, scan electrode wiring, and signal electrode wiring
4 and peripheral circuit section 203 for driving the matrix section
Etc. are provided on the substrate 100. Also, 201,2
Reference numeral 02 is a sealing member. Of these, 202 is a sealing member for the liquid crystal 206, and 201 is a sealing member for sealing the peripheral circuit portion 203. The sealing members 201 and 202 are on the non-translucent layer 107, respectively.

In the liquid crystal element shown in FIG. 2, which is one embodiment of the present invention, not only the active matrix section 204 but also the peripheral circuit section 2 is provided between both substrates (100, 200).
Since the semiconductor device No. 03 is also interposed, both substrates serve as protective members for peripheral circuits.

[0021]

EXAMPLES Hereinafter, each example of the present invention will be described, but the present invention is not limited to these examples, and design changes of each component within the scope of achieving the object of the present invention. It also includes those in which each member is replaced.

Example 1 FIGS. 3A to 3D show a method for producing a liquid crystal device of Example 1 according to the present invention. A glass having a difference in thermal expansion coefficient of 5% or less with respect to the Si wafer with TFT as one substrate and the Si wafer as the opposite substrate (AL manufactured by Asahi Glass Co., Ltd.) is used.

According to the present embodiment, as described in detail below, the UV curable resin is temporarily fixed on the substrate, and the encapsulant made of the thermosetting resin is completely cured by thermosetting while preventing misalignment. Let As a result, the difference in the coefficient of thermal expansion of the substrate is clearly within ± 50%, and 2
It is possible to prevent misalignment (alignment misalignment) by curing one.

First, as shown in FIG. 3A, in order to maintain a predetermined thickness for sealing at a predetermined position on the substrate 1 ', a grain size of 6 μm is used.
Place the spacer (not shown). A thermosetting adhesive (sealant) 2 is formed on the substrate 1 by screen printing. On the other hand, on the substrate 1 ', a spherical diameter 7 for maintaining a predetermined substrate space
After spraying the resin balls (spacing material) 3 of μ, the ultraviolet curable adhesive 6 is applied to a predetermined position outside the area finally used as a liquid crystal display by a precision discharge device by about 0.5 mm ² . .. Next, as shown in FIG. 3 (b), superposition marks (not shown) formed at the time of forming electrodes on both substrates are superposed at a predetermined position by using a superposition device while observing with a microscope. After the positioning is completed, as shown in FIG. 3C, 0.5 kgf / cm ^{2 in} the direction of arrow 4.
Press uniformly over the entire substrate with moderate pressure. When the thickness of the sealant reaches almost the specified value, while checking the overlay mark again, the UV curing applied using a spot exposure device with an irradiation area of about 10 mm from the UV irradiation gap cut out in the press The mold adhesive 6 is irradiated with ultraviolet rays 7 to cure the adhesive 6. The steps of superimposing → positioning → press → ultraviolet irradiation are processed in the same apparatus. Next, check the position of the stack and
The substrate is heated by a heater 8 under a pressure 4 ′ of about 0.5 kgf / cm ² using a heating press device as shown in FIG. 1 (d).
At 170 ° C., the sealant is cured.

(Embodiment 2) FIG. 4 is a partial sectional view of a liquid crystal element according to Embodiment 2 of the present invention, and Embodiment 2 relates to application to a color liquid crystal display device. TFT
The attached substrate is a Si wafer, and the opposite substrate is glass with a difference in thermal expansion coefficient of ± 5% or less (NH Techno Glass Co., Ltd.
A-35) was used. In the second embodiment, the color filter layer 14 is formed on the counter substrate 11 by repeating the following steps of a, b, c and d five times to form R, G and B, respectively. Step a: forming a dyed substrate on the entire surface by spin coating,
Make a predetermined pattern. Step b: Color with a dye having a predetermined spectral characteristic. Step c: A protective film is formed on the entire surface of the substrate by spin coating. Step d: The protective film 14a is patterned to remove the protective film in a region (hereinafter referred to as a seal area) in contact with the peripheral sealing agent 15.

Next, a common electrode 1 is formed by forming ITO on the color filter layer 14 and the protective film 14a by a sputtering method.
6

The method of forming the protective film is not limited to patterning and may be any method as long as the protective film is not formed in the seal area, and examples thereof include a roll coating method, a screen printing method, a mask vapor deposition method and a mask sputtering method.

On the other hand, the pixel electrode 12 connected to the TFT is formed on the substrate 13.

The alignment film 1 is formed on each of the pair of substrates.
After forming No. 7 by a roll coating method or various printing methods, rubbing treatment is performed.

Then, an ultraviolet curable resin mixed with a spacer 18 as a sealant 15 is formed on one of the substrates by screen printing. Next, the pair of substrates are bonded together, pressed, and then irradiated with ultraviolet rays to cure the sealant to form a liquid crystal cell, and the liquid crystal 19 is sealed therein to obtain a liquid crystal display panel.

In the second embodiment described above, it is possible to prevent the positional deviation of the substrate and the pixel by selecting the substrate, and further, the color filter layer is formed except for the portion in contact with the sealant, and the sealant is directly contacted with the common electrode. As a result, the spacer is not easily embedded in the color filter layer, and the cell gap of the liquid crystal can be easily controlled.
Further, the absorption of ultraviolet rays by the color filter layer is eliminated, the ultraviolet-curable sealing agent can be cured in a short time, and the uncured sealing agent can be prevented. Further, the adhesiveness of the sealant is also improved, and the reliability is greatly improved.

(Third Embodiment) The third embodiment is a modification of the first embodiment.

In the third embodiment, the TFT substrate 1'is made of Si.
As the wafer and the counter substrate 1, glass having a difference in coefficient of thermal expansion of ± 5% or less (# 1733 manufactured by Corning Co., Ltd.) was used, a UV curable resin was used as a sealant, and a spacer was mixed only in the seal part (pixels. A cell assembly is carried out in the same manner as in Example 1 except that the spacing material 3 is not sprinkled on the parts. According to the present embodiment, misalignment can be prevented by selecting the substrate, and the heating condition at the time of cell assembly can be eased by using only the UV curing resin as the sealant. In addition, the display quality is improved because the spacer is mixed only with the sealant and is not scattered on the display part.

(Embodiment 4) In this embodiment 4, Corning # 1727 (coefficient of thermal expansion: 44 × 10 ⁻⁷ ) having a thickness of 0.5 μm is used.
/ ° C) and then a predetermined electrode is formed on the surface on which no electrode is formed with an epoxy resin and a thickness of 0.5 μ is manufactured by Corning Co.
TF made of Si wafer on the # 1727 side of the counter substrate to which 733 (coefficient of thermal expansion: 36.5 × 10 ⁻⁷ / ° C.) is bonded.
The cell set is performed on the T substrate side. According to the present embodiment, glass having a different thermal expansion coefficient is bonded as the opposite substrate to obtain glass having a thermal expansion coefficient on the + side of the Si wafer, so that the stress applied to the Si wafer after the cell assembly is used as the tensile stress. be able to.

In each of the embodiments described above, quartz glass can be used as the substrate with the TFT in addition to the Si wafer. However, particularly preferred is a Si substrate manufactured by the method shown in FIG. The Si substrate is a Si single crystal substrate which is excellent in economy and has an extremely excellent crystallinity which is uniform and flat over a large area, and a semiconductor active element is formed on a Si single crystal layer having a significantly small number of defects. Therefore, the stray capacitance of the semiconductor element is reduced, high-speed operation is possible, and a high-performance liquid crystal in which elements and circuits excellent in radiation resistance without latch-up phenomenon are integrated on the same substrate as the liquid crystal image display pixel. A display can be provided.

An example of the method for manufacturing the Si substrate will be described below with reference to FIG.

A P-type (10
0) A single crystal Si substrate is anodized in an HF solution to form a porous Si substrate.

The above anodization conditions were as follows.

Applied voltage: 2.6 (V) Current density: 30 (mA · cm ^-2 ) Anodizing solution: HF: H ₂ O: C ₂ H ₅ OH = 1:
1: 1 time: 2.4 (hour) Porous Si thickness: 300 (μm) Porosity: 56 (%) P-type (100) porous Si substrate 101 thus obtained
The Si epitaxial layer 102 is formed on the upper surface by low pressure CVD.
Are grown with a layer thickness of 1.0 micron. The deposition conditions are as follows.

Source gas: SiH ₄ carrier gas: H ₂ Temperature: 850 ° C. Pressure: 1 × 10 ^-2 Torr Growth rate: 3.3 nm / sec Next, a 1000 angstrom oxide layer 103 is formed on the surface of the epitaxial layer 102. Forming an oxide layer 104 of 5000 angstroms on the surface,
The other Si substrate 107 on which the nitride layer 105 of 1000 angstrom is formed is laid on top of one another and placed in a nitrogen atmosphere for 8 hours.
By heating at 00 ° C. for 0.5 hour, the two Si substrates are firmly bonded together.

Then, the bonded substrates are mixed with a mixed solution of 49% hydrofluoric acid, alcohol and 30% hydrogen peroxide (10:
The selective etching was carried out in the 6:50) without stirring.
After 65 minutes, only the non-porous Si layer remains without being etched, and the single crystal Si is used as an etch stop material.
The porous Si substrate 101 was selectively etched and completely removed. The etching rate of the non-porous Si single crystal with respect to the etching solution is extremely low, the etching layer is 50 angstroms or less even after 65 minutes, and the selectivity with the etching rate of the porous layer reaches 10 5 or less, The etching amount (tens of angstroms) in the non-porous layer is practically negligible. In this way, porous Si having a thickness of 200 microns is obtained.
Substrate 101 was removed and 1.0 μ on SiO ₂ 103
A single crystal Si layer 102 having a thickness of m can be formed. When SiH ₂ Cl is used as the source gas, it is necessary to raise the growth temperature by several tens of degrees, but the enhanced etching characteristic peculiar to the porous substrate is maintained.

A TFT is formed on the single-crystal silicon thin film 102, and thereafter, a Si substrate side is covered with a hydrofluoric acid resistant rubber except under the liquid crystal pixel portion, and a mixed solution of hydrofluoric acid, acetic acid and nitric acid is used. The silicon substrate is partially removed up to the insulating layer to form the light transmission part 110.

Thus, the TFT as shown in FIG.
The attached substrate is produced.

(Embodiment 5) FIG. 6 is a schematic view for explaining a method of manufacturing a liquid crystal element according to Embodiment 5 of the present invention.

In the present invention, a light-transmitting substrate such as quartz glass or an opaque substrate such as Si wafer is used as one substrate, and the opposite substrate has a difference in coefficient of thermal expansion from the quartz glass or Si wafer. A light-transmitting substrate having a thermal expansion coefficient within ± 5% is used. Moreover, a plurality of semiconductor island regions are provided on one substrate, and active elements such as TFTs are formed therein.

As shown in step (a) of FIG. 6, the porous layer 101 is formed by either partially making the single crystal substrate porous or epitaxially growing a semiconductor layer on the porous semiconductor substrate. A substrate having a semiconductor layer thereon is prepared.

On the other hand, as shown in step (a) of FIG. 6, a substrate made of quartz glass or a substrate having an insulating film on a silicon wafer is prepared. Then, as shown in step (b) of FIG. 6, the above-mentioned both substrates are bonded together. Where 104
Is an insulating layer, which is a partial region of the substrate 107 in the case of quartz glass, and corresponds to the silicon oxide film formed on the surface in the case of a Si wafer.

Next, as shown in step (c) of FIG. 6, the porous layer 101 is removed by etching by selective etching. A mixed liquid of hydrofluoric acid, alcohol, and hydrogen peroxide water, which serves as an etchant, can provide a large selection ratio between the porous layer 101 and the semiconductor layer (not porous) 102, and enables the selective etching.

Element isolation regions 210 are formed in the semiconductor layer 102 obtained as shown in step (d) of FIG. 6, and active elements constituting the active matrix are formed in the regions 204.
Then, elements forming peripheral circuits are formed in the region 203.

Next, as shown in step (e) of FIG. 6, the counter substrate 2 having substantially the same area (planar area) as the substrate 107.
Glass is bonded as 00 through the sealant 202. Then, the liquid crystal material 206 is injected and sealed between the substrate 200 and the substrate 107. Here, since the substrate 200 has substantially the same surface area as the substrate 107, the end portion of the substrate 200 is located on the region 203 and serves as a protective layer for peripheral circuits.

FIG. 7 shows the substrate 10 in the step (e) of FIG.
7 is a schematic top view for explaining the step of attaching 7 and the substrate 200. FIG.

Of course, when a light transmissive liquid crystal element is manufactured using a Si wafer as a substrate, a part of the substrate 107 may be removed to form a light transmissive portion as shown in FIGS. ..

FIG. 8 is a schematic diagram showing an image information processing apparatus using a liquid crystal element according to the present invention.

Reference numeral 300 is a liquid crystal element, and a display portion 310 is provided in the center thereof. In FIG. 8, the active matrix portion is schematically shown as an enlarged view 204. Peripheral circuits including shift registers are arranged in a region 203 around the display unit 310. Among the peripheral circuits, horizontal driving circuits connected to signal lines and supplying video signals are arranged above and below the display unit 310, and driving circuits connected to gate lines and generating line selection signals are arranged on the left and right sides of the display unit 310. .

These drive circuits are connected to and controlled by a drive control circuit 410 mounted on another board.

The drive control circuit 410 is connected to a central control circuit 414 together with a lighting control circuit 411 including a light source 412 and an inverter for controlling lighting of the light source.

Further, this image information processing apparatus has an optical system 422 including a lens for inputting image information, an image sensor 421 including a photoelectric conversion element, and a drive circuit 420 thereof.

In addition, the image information by the image sensor 421 and / or the displayed image information is recorded by the recording head 431.
The data is recorded on the recording medium by the recording control circuit 430 including.

FIG. 9 is a schematic top view for explaining a connection portion between the liquid crystal element of the present invention and the drive control circuit 410 shown in FIG.

In FIG. 9, the lower substrate 170 and the upper substrate 200 are made different in size so that the wiring pad portion 406 of the lower substrate protrudes from the upper substrate 200. The pad portion 406 is connected to the drive control circuit 410 via the flexible wiring 405. Of course, in this case as well, the peripheral circuit semiconductor element portion on the substrate 107 is the upper substrate 2
It is covered with 00 and protected.

Thus, when a liquid crystal element is used as a display element, an image signal is supplied from a circuit 410 on another substrate to a peripheral circuit via a flexible wiring 405 to display an image.

[0062]

As described above, according to the present invention, the influence of the thermal history in the process of assembling the substrates is reduced by keeping the difference in the coefficient of thermal expansion between the two substrates within ± 50%.
The process temperature constraint in the process is relaxed.

Specifically, when a thermosetting sealant is used as the sealant, the sealant is usually cured at 150 to 200 ° C. Therefore, in the conventional configuration, the bonding accuracy of the upper and lower substrates in this process is However, according to the present invention, this pixel shift can be prevented by keeping the difference in coefficient of thermal expansion within ± 50%.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing one of a pair of substrates used in the present invention,

FIG. 2 is a schematic cross-sectional view showing an example of a liquid crystal element according to the present invention,

FIG. 3 is a schematic diagram for explaining a manufacturing process of a liquid crystal element according to Example 1 of the present invention,

FIG. 4 is a schematic cross-sectional view showing a part of a liquid crystal element according to Example 2 of the present invention,

FIG. 5 is a schematic diagram for explaining a manufacturing process of a substrate used in the present invention,

FIG. 6 is a schematic diagram for explaining a manufacturing process of a liquid crystal element according to a fifth embodiment of the present invention,

FIG. 7 is a schematic top view for explaining a liquid crystal element according to Example 5,

FIG. 8 is a schematic diagram for explaining an image information processing apparatus using a liquid crystal element according to the present invention,

FIG. 9 is a schematic top view for explaining the connection between the liquid crystal element of the present invention and the drive control circuit.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Moriyuki Okamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yu Kamio 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (7)

[Claims] 1. In a liquid crystal element in which two substrates are opposed to each other at a predetermined interval and liquid crystal is sealed between them, the materials of the two substrates are different, and the difference in coefficient of thermal expansion between the two substrates is the heat of one substrate. A liquid crystal element having a coefficient of expansion within ± 50%. 2. The liquid crystal device according to claim 1, wherein one of the two substrates is a quartz substrate or a semiconductor substrate. 3. The liquid crystal device according to claim 1, wherein one of the two substrates is a silicon substrate having a light transmitting portion. 4. The liquid crystal element according to claim 1, wherein one of the two substrates is a substrate having a semiconductor integrated circuit, and the other substrate is arranged so as to cover the semiconductor element of the circuit. 5. Two substrates are made to face each other at a predetermined interval, liquid crystal is sealed between them, the materials of the two substrates are different, and the difference in the coefficient of thermal expansion between the two substrates is equal to the coefficient of thermal expansion of one substrate. An image information processing apparatus comprising: a liquid crystal element within ± 50%; and an image signal generation circuit provided separately from the substrate for supplying an image signal input to the element. 6. The image information processing apparatus according to claim 5, wherein the image information processing apparatus further includes an image sensor that generates information that is a basis of the image signal. 7. The image information processing apparatus according to claim 5, further comprising recording means for recording information according to the image signal on a recording medium.